1. Field of the Invention
The present invention relates to a disk cartridge having a cartridge housing in which a disk-like recording medium such as an optical disk, a magnetooptical disk and a magnetic disk is stored in a disk compartment so as to become freely rotatable, and particularly to a disk cartridge in which a pair of shutter members are opened and closed to open and close an opening portion by rotating a middle shell which forms a disk compartment between it and an upper shell or a lower shell and a part of a disk-like recording medium is exposed from the opening portion when the opening portion is opened.
2. Description of the Related Art
As a disk cartridge in which a disk-like recording medium in and/or from which audio information, video information or information such as computer data can be recorded and/or reproduced is rotatably stored in a cartridge housing, there is known a disk cartridge having an arrangement shown in FIG. 27, for example. This disk cartridge 1 is a disk cartridge incorporating therein a write once magnetooptical disk 4 in which a user can record and write information such as computer data later on. This disk cartridge has an appearance shown in FIG. 27.
This disk cartridge 1 includes a cartridge housing 2 comprised of a pair of an upper shell 2a and a lower shell 2b, a magnetooptical disk 4 rotatably stored within a disk compartment 3 of this cartridge housing, and the like. The cartridge housing 2 has on its upper and lower surfaces an upper and lower opening portion 5 which is extended from the central portion to one side. This opening portion 5 can be opened and closed by a shutter member 6 which can be slid along one side. Reference numeral 6a designates a presser member which can prevent the tip end portion of the shutter member 6 from being extracted.
A disk-like metal center hub 7 is provided at the central portion of the magnetooptical disk 4. This center hub 7 is disposed at the position opposing to the inner end portion of the opening portion 5, i.e., at substantially the central portion of the cartridge housing 2. A turntable provided on an information recording and reproducing apparatus body side is mounted on this center hub 7 and the magnetooptical disk 4 is fixed to the center hub by chucking of the turntable, whereby the magnetooptical disk 4 is rotated at a predetermined velocity (e.g., constant linear velocity). In this case, an information signal is recorded on or reproduced from the magnetooptical disk 4 by action of a magnetooptical pickup device whose head portion is inserted into the opening portion 5.
However, in the conventional disk cartridge having the above arrangement, the shutter member 6 which opens and closes the opening portion 5 has a U-like shaped cross-section. This shutter member 6 is fitted into one side of the cartridge housing 2 and the shutter member 6 is slid along one side of the cartridge housing to thereby open and close the opening portion 5 For this reason, it is unavoidable that a large space is produced between the cartridge housing 2 and the shutter member 6, and therefore the disk cartridge cannot be prevented from being smudged by very small dusts particles and the like.
In recent years in the stream in which an optical disk is increasing its storage capacity/increasing its recording density, a recording pattern is becoming narrower in pitch and is increasing in linear density. When a recording surface of an optical disk or a magnetooptical disk is smudged by dusts, the read or write beam is shielded, also when the information recording surface of the optical disk is damaged by scratches, information cannot be read or written normally. For this reason, in the conventional disk cartridge, as shown in FIG. 27, the shutter member 6 having substantially the U-like shaped cross-section is attached to one side of the cartridge housing 2 so as to become slidable and is slid along one side of the cartridge housing thereby to open and close the opening portion 5 so that the information recording surface of the optical disk or the like can be protected.
However, as the optical disk is further increased in storage capacity or recording density, very small dusts particles which are not so influential in the prior art becomes more influential over reading and writing of data. Therefore, the shutter member having the above U-like shape cannot prevent the disk cartridge from being smudged by very small dusts particles. In this case, when the information recording surface of the magnetooptical disk 4 is smudged by very small dusts particles entering into the cartridge housing 2, the information recording surface of the magnetooptical disk is damaged by dusts so that information cannot be read out from and written in the magnetooptical disk normally.
In the above conventional disk cartridge 1, the shutter member 6 is located on the disk cartridge at its position in which users can easily touch the shutter member. There is then the risk that a user will slide the shutter member 6 to open the opening portion 5 by mistake. In addition, since the shutter member 6 is linearly slid along one side of the cartridge housing 2, there arises a problem that the surface area of the cartridge housing 2 cannot be reduced.